The defendant, who remains free pending a November sentencing date, faces as much as 18 months behind bars under a plea deal (.pdf) with Massachusetts federal authorities.

Among other exploits, Andrew James Miller pleaded guilty to propositioning an undercover Federal Bureau of Investigation agent during an online chat to pay him $50,000 for “root” access to the supercomputers at the National Energy Research Scientific Computing Center at the Lawrence Berkeley National Lab California.

Using the handle “Green,” he pasted during the chat that he had proof of access, the government said in an indictment. The research center, which houses some of the world’s most powerful computers, offers high-end computing power for Energy Department-approved projects.

The defendant, a member of the hacking group Underground Intelligence Agency, was arrested and indicted (.pdf) in June. A fellow member of the group, Robert Burns, who went by the handle “Intel,” assisted authorities with the prosecution, court documents show.

Miller gained access to the supercomputers via hacking into a Japanese university that had connections to those computers, the government said. Miller told FBI agents that he also had access to the supercomputers via Harvard University and the University of California at Davis.

The feds never paid him the $50,000, according to court records. (.pdf)

According to court documents, the defendant bragged to FBI agents online that he had broken into the corporate servers of American Express, Yahoo, Google, Adobe, WordPress and other companies and universities.

The authorities said they paid him $1,000, via Western Union, for access to the entire corporate network of RNKTel, a Massachusetts-based telco.

“According to RNKTel, with that administrator-level access, a bad actor could not only have accessed RNKTel’s confidential business records but could also have altered customer accounts to obtain, for free, the telecommunication services that RNKTel sells to its customers,” prosecutors said.

For $1,200, the FBI bought from Miller a database of thousands of log-in credentials of the ISP Layered Tech of Texas. Miller also sold the FBI — for $1,000 — access to the domain of the Domino’s Pizza chain, according to court records.